fix(query): reducing size of proto execution plans

[kvpetrov]

Pull Request checklist

• [ X ] The commit(s) message(s) follows the contribution guidelines ?
• [ X ] Tests for the changes have been added (for bug fixes / features) ?
• Docs have been added / updated (for bug fixes / features) ?

Current behavior :
Execution plans contain query context that can be repeated multiple times.

New behavior :
Taking the query context out of the protobuf execution plans and sending the context separately.

BREAKING CHANGES
The feature should be turned on only after full rollout. FiloDBs, QueryServers with the new version cannot talk to the older version.

Other information:

[yu-shipit]

just wondering if we can customized the serialization/deserialization to avoid the protocol change.